And Nadab and Abihu, the sons of Aaron, took each of them his censer, and put fire therein, and laid incense thereon, and offered strange fire before the Eternal, which He had not commanded them. And there came forth fire from before the Eternal and devoured them, and they died before the Eternal. (Exodus 10:1-2)
And Aaron spoke unto Moses: ‘Behold, this day have they offered their sin-offering and their burnt-offering before the Eternal, and there have befallen me such things as these; and if I had eaten the sin-offering to-day, would it have been well-pleasing in the sight of the Eternal? And when Moses heard that, it was well-pleasing in his sight. (Leviticus 10:19)
The Torah Portion Shemini tells two stories: One of the tragic death of two sons of Aaron—Nadab (Nadav) and Abihu (Avihu) and the other of conflict between Moses and Aaron. What is the common thread that connects these two stories? As we shall see, it is all about time.
The story of Nadab and Abihu is not easy to understand. These were two righteous and holy people. Commenting on the tragic death of Nadab and Abihu, Moses tells his brother Aaron:
This is it that the Eternal spoke, saying: Through them that are nigh unto Me I will be sanctified, and before all the people I will be glorified.” (Exodus 10:3)
Rashi explains this verse to mean that Nadab and Abihu were even greater tzadikim than Moses and Aaron. All they wanted to do was serve G‑d. Even if they made a procedural mistake by bringing unauthorized fire to the Altar, why did they deserve such a harsh punishment?
To understand, we need to examine the inner meaning of their error. The Chasidic philosophy teaches that our soul has an internal rhythm—called in Hebrew ratzo vashov, i.e., running and returning or rushing up and settling down. This idea is based on the prophecy of Ezekiel in Ma’ase Merkavah, who saw angelic beings running and returning:
And the living creatures ran and returned as the appearance of a flash of lightning.” (Ezekiel 1:14)
This rhythm ratzo vashov manifests physically in the rhythm of life—the breathing cycle, breathing in and breathing out, as well as in the beating of the heart resulting from the heart’s rhythmic contraction and expansion. Spiritually, ratzo vashov is the oscillation of the soul between running up to G‑d, as it were, seeking to unite with its Creator in the ecstasy of unio mystica (devekut) and returning to the body, settling down to do its job of elevating and rectifying this physical world. Chasidic teachings warn us that left unchecked, the desire for spiritual ecstasy, ratzo, can lead to klot hanefesh—the expiration of the soul. Generally, Judaism does not emphasize spiritual enlightenment and unio mystica for its own sake. Rather, Judaism emphasizing the Divine service in elevating this world and making dirah b’tachtonim—a dwelling place for G‑d down here. Spiritual excitement and enlightenment are seen in Judaism as a means to an end, which is a life in a body engaged in the rectification of this world. The momentary ecstasy of the ratzo is meant only to inspire the soul to return to the body, shove, to complete its earthly task. According to the teachings of Chassidism, the mistake of Nadab and Abihu was in seeking the ecstasy of unio mystica for its own sake, neglecting their ultimate mission of serving G‑d in the physical world. Mistake as it was, why did it warrant punishment by death?
To understand that, we need to recall another Chasidic teaching that sees the rhythm of ratzo vashov as the source of time (see more on this in my essays “On the Nature of Time and the Age of the Universe” and “Cosmic Symphony”). Briefly, as the mirror reflection of the Divine rhythm of mati velo mati—i.e., “reaching and not reaching,” expansion and contraction—the rhythm ratzo vashov, running and returning, precedes the creation of time (zman) and is viewed as the ultimate source of seder hazmanim, “the order of times,” which, in turn, is the source of time as we know it.
The smallest element of time, or the quanta of time, if you will, is a complete cycle of ratzo vashov. By emphasizing only one half of the cycle—ratzo—and neglecting the other half—shov—Nadab and Abihu strived to reach the level above time. They placed themselves outside of the rhythm of time and therefore, the rhythm of life. As it turns out, Nadab and Abihu were not punished by G‑d. Rather, they committed spiritual suicide, ratzo without shov, resulting in their physical demise.
Let us now turn to the other story, the conflict between Moses and Aaron. What prompted the dispute? After Nadab and Abihu died, Aaron’s two surviving sons, Elazar and Ithamar, became ineligible to serve in the Mishkan (the Tabernacle). Moreover, as mourners, both Aaron and his surviving sons were prohibited from eating sacrifices.
Recall that all this happened on a very festive day—the eighth and final day of Mishkan’s inauguration. Not wishing to disrupt the celebration of the Tabernacle’s inauguration, G‑d commanded Moses to instruct Aaron and his sons to bring and eat a meal-offering notwithstanding their status or mourners, which they did. Aaron and his sons also brought two other sacrifices, which were part of the Tabernacle’s inauguration. However, upon noticing that a third sacrifice, the sin-offering goat, was burnt rather than eaten, Moses became angry. He confronted Aaron, Eleazar, and Ithamar demanding to know why they did not partake of this sacrifice. Aaron stood his ground and explained that he deemed this particular sacrifice different from the rest. The other sacrifices, which he and his sons ate despite being mourners, were mitzvot de jour—i.e., one-time commandments of the day as part of the Mishkan’s inauguration ceremony. However, the uneaten sacrifice was a regular offering, brought every New Moon (Rosh Chodesh). This explanation found favor in Moses’s eyes and he admitted that Aaron was in the right. What’s going on here?
Perhaps, the exchange between Moses and Aaron can also be explained through the prism of time. Those offerings that Aaron and his sons ate were one-time offerings and thus, not connected with the concept of time. However, a regular offering that is periodically repeated is very much connected with the notion of time, the nature of which is the periodicity sourced in the ratzo vashov rhythm.
How much more so this was true of that specific offering that was burned and not eaten, as that was a regular Rosh Chodesh offering. Recall that the first commandment given to Jews was the commandment to keep the calendar (essentially, to keep time) by counting New Moons, Roshei Chodashim. Thus, the Rosh Chodesh offering that Moses complained about was the offering directly connected to the Rosh Chodesh celebration, as part of the commandment to recon time! Aaron and his two surviving sons were in a state of mourning after the death of Aarons elder sons, Nadab and Abihu. As I explained in my essay “Paradox of the Red Heifer,” the cessation of life is synonymous with the cessation of time—a person stops living when his internal clock stops. Thus, life itself is almost synonymous with time. How could then they carry out Rosh Chodesh observances intended to recon time, reasoned Aaron, when he and his sons were mourning the death of his two older sons for whom the time stopped?
This explanation also helps us understand why Moses, who was initially angry at the perceived infraction, was so satisfied with Aaron’s explanation. It goes far beyond, it seems, the purely halahic (legalistic) decision of Aaron. Moses was pleased with Aaron’s explanation because he realized that Aaron understood the mistake of his elder sons, who denied time by neglecting the second half of the ratzo vashov cycle. By distinguishing between occasional offerings and regular offerings, something that escaped even Moses at that moment, Aaron alluded to the essential rhythm of time, thereby rectifying the error of his sons.
Time, as it turns out, is the common thread connecting these two stories. They emphasize the utmost importance of time in our individual lives, as well as in the functioning of the Mishkan, which represents the spiritual life of the entire community. If we learn this critical lesson from the tragic story of the death of Nadab and Abihu, their death will not have been for naught.
 See, Rabbi Shalom Dovbaer Schneerson, Hemshech Samach Vav.
 Rabbi Shneur Zalman of Liadi identifies seder hazmanim with the six midot (lower sefirot—Chesed, Gevurah, Tiferet, Netzach, Hod, and Yesod) of the World of Emanation, the Atzilut. (see for example, Maamarei Admur HaZaken, Ki Teitze)
 As the Kohen Gadol (High Priest), Aaron was eligible to serve and bring sacrifices despite being in mourning, but this distinction does not extend to eating the sacrifices.